U.S. patent application number 12/052923 was filed with the patent office on 2008-10-09 for optical particle sensor with exhaust-cooled optical source.
Invention is credited to Rick Miller.
Application Number | 20080246965 12/052923 |
Document ID | / |
Family ID | 39788948 |
Filed Date | 2008-10-09 |
United States Patent
Application |
20080246965 |
Kind Code |
A1 |
Miller; Rick |
October 9, 2008 |
Optical Particle Sensor with Exhaust-Cooled Optical Source
Abstract
The invention relates to particle sensors that are capable of
passively cooling high-powered optical sources within the sensor,
thereby extending the optical source lifetime without requiring
additional power. The sensor detects particles within a sample
fluid by optical interaction of the optical source with flowing
sample fluid in the sample chamber. Sample fluid that exits the
sample chamber is directed into thermal contact with the optical
source, thereby cooling the optical source. Sample fluid that has
come into thermal contact with the optical source is continuously
removed from the sensor to ensure the optical source is adequately
cooled. A variety of elements are used to facilitate thermal
contact between the optical source and sample fluid including
plenums, heat sinks, and airflow cavities. Provided are related
methods for cooling a one or more heat-producing device within a
particle sensor.
Inventors: |
Miller; Rick; (Loveland,
CO) |
Correspondence
Address: |
GREENLEE WINNER AND SULLIVAN P C
4875 PEARL EAST CIRCLE, SUITE 200
BOULDER
CO
80301
US
|
Family ID: |
39788948 |
Appl. No.: |
12/052923 |
Filed: |
March 21, 2008 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60896649 |
Mar 23, 2007 |
|
|
|
Current U.S.
Class: |
356/337 ;
356/246 |
Current CPC
Class: |
G01N 15/0205 20130101;
G01N 2001/2282 20130101 |
Class at
Publication: |
356/337 ;
356/246 |
International
Class: |
G01N 21/00 20060101
G01N021/00; G01N 1/10 20060101 G01N001/10 |
Claims
1. A particle sensor for sensing particles in a fluid sample, said
sensor comprising: a. a sample chamber having an inlet orifice for
receiving a flow of said fluid sample and an outlet orifice for
conducting said fluid sample out of said sample chamber; b. an
optical source provided in optical communication with said sample
chamber; and c. an outlet passage in fluid communication with said
outlet orifice for receiving at least a portion of said flow of
fluid sample from said sample chamber; said outlet passage having a
portion in thermal contact with said optical source; wherein
thermal exchange between said flow of sample fluid in said outlet
passage and said optical source is capable of cooling said optical
source.
2. The sensor of claim 1, wherein said optical source is a laser
having a power consumption that is equal to or greater than 100
mW.
3. The sensor of claim 1, wherein said optical source has an
operating temperature and said fluid sample has a fluid sample
temperature, and said thermal exchange between said flow of sample
fluid in said outlet passage and said optical source is capable of
maintaining said optical source operating temperature within about
5 degrees Celsius of said fluid sample temperature.
4. The sensor of claim 3, wherein said fluid sample at said sample
chamber outlet has a temperature selected from a range of between
about 20.degree. C. and about 30.degree. C.
5. The sensor of claim 1, wherein the temperature of said flowing
sample fluid in said outlet passage is between about 3.degree. C.
to 8.degree. C. less than said optical source operating
temperature.
6. The sensor of claim 1 wherein said outlet passage is capable of
transmitting said flow of fluid sample at flow rates selected from
the range of greater than and equal to 25 L/min and less than or
equal to 100 L/minute.
7. The sensor of claim 1 having a chamber pressure in said sample
chamber and an outlet pressure in said outlet passage, wherein said
chamber pressure and said outlet pressure are within about 10% of
each other.
8. The sensor of claim 1 further comprising a mounting element that
supports said optical source, wherein a portion of said outlet
passage is in physical contact with said mounting element.
9. The sensor of claim 1, wherein said outlet passage further
comprises a second portion in thermal contact with a
heat-generating device.
10. The sensor of claim 9, wherein said outlet passage further
comprises a junction, wherein said junction divides said flow of
fluid sample into a plurality of flowpaths for cooling a plurality
of said heat-generating device.
11. The sensor of claim 10, wherein said junction divides said flow
of fluid sample into two flowpaths, wherein a first flowpath is
capable of cooling said optical source, and a second flowpath is
capable of cooling a heat-generating device.
12. The sensor of claim 11, wherein said heat-generating device is
a blower motor.
13. The sensor of claim 9, wherein the heat-generating device is
selected from the group consisting of a power source, motor, pump,
optical component, regenerative blower and fan.
14. The apparatus of claim 1, wherein said outlet passage portion
in thermal contact with said optical source comprises a plenum.
15. The sensor of claim 14, wherein said plenum has a surface area
in thermal contact with said optical source that is greater than
about 650 mm.sup.2.
16. The sensor of claim 14, wherein said fluid sample within said
plenum has a Reynolds number selected from a range of 2200 and
2900.
17. The sensor of claim 14 having an optical source mount for
connecting said optical source to said sensor, wherein said plenum
is connected to said optical source mount.
18. The sensor of claim 17, wherein said optical source mount has
an exterior surface and said plenum has at least one surface that
corresponds to said optical source mount exterior surface.
19. The sensor of claim 18, wherein said plenum surface that
corresponds to said optical source mount exterior surface has a
surface area selected from a range of between about 650 mm.sup.2
and 1500 mm.sup.2.
20. The sensor of claim 14, wherein said plenum further comprises:
a. a plenum inlet orifice for receiving flow of said fluid sample;
b. a plenum outlet orifice for conducting said fluid sample out of
said plenum; c. inlet tubing having a first end connected to said
plenum inlet orifice and a second end connected to said sample
chamber outlet or said outlet passage for introducing sample fluid
to said plenum inlet orifice; and d. outlet tubing having a first
end connected to said plenum outlet orifice and a second end
connected to an exhaust orifice for transporting fluid sample out
of said sensor.
21. The sensor of claim 20 having an optical source operating
temperature, wherein said fluid sample at said plenum inlet orifice
has a temperature that is selected from about 5.degree. C. to about
10.degree. C. less than said optical source operating
temperature.
22. The sensor of claim 14 comprising a plurality of plenums,
wherein each plenum is in thermal contact with said optical
source.
23. The sensor of claim 1 having an optical source operating
temperature, wherein said outlet passage portion in thermal contact
with said optical source comprises a heat sink having an inlet heat
sink orifice and outlet heat sink orifice, said fluid sample at
said inlet heat sink orifice having an inlet temperature, wherein
said inlet temperature is less than said optical source operating
temperature.
24. The sensor of claim 23, wherein said heat sink comprises one or
more heat transfer passages.
25. The sensor of claim 24, wherein said heat transfer passage has
a geometric shape selected from the group consisting of a
serpentine, spiral, fin, chamber, rectangular bore and circular
bore.
26. The sensor of claim 24 comprising a plurality of heat transfer
passages that are connected in a parallel configuration to said
inlet heat sink orifice and said outlet heat sink orifice, thereby
introducing and removing flowing fluid sample from each of said
heat transfer passages; wherein said flowing sample fluid within
said heat transfer passages are capable of conveying heat generated
by the optical source to said exhaust outlet thereby cooling said
optical source.
27. The sensor of claim 1, wherein said outlet passage portion in
thermal contact with said optical source is separated from said
optical source by a separation distance that is less than about 2
cm.
28. The sensor of claim 1, wherein said thermal contact portion is
capable of sustaining an the optical source at a temperature that
is between about 5.degree. C. to about 15.degree. C. less than a
corresponding optical source temperature in a conventional
sensor.
29. The sensor of claim 1, wherein said outlet passage in thermal
contact with said optical source is configured in a cross-flow
geometry relative to said optical source.
30. A method for cooling an optical source of a particle sensor
comprising: a. providing said particle sensor comprising: i. a
sample chamber having an inlet orifice for receiving an input flow
of said fluid sample and an outlet orifice for conducting an
exhaust flow said fluid sample out of said sample chamber; and ii.
an optical source provided in optical communication with said
sample chamber; and b. providing an outlet passage in fluid
communication with said outlet orifice of said sample chamber for
receiving at least a portion of said exhaust flow of said fluid
sample from said sample chamber; said outlet passage having a
portion in thermal contact with said optical source; and c. flowing
said fluid sample through said sample chamber and said outlet
passage, thereby generating said input flow of sample fluid and
said exhaust flow of sample fluid; wherein thermal exchange between
said at least a portion of exhaust flow of sample fluid flowing
through said outlet passage and said optical source cools said
optical source.
31. The method of claim 30, wherein said optical source is
connected to said particle counter by an optical source mount, and
said outlet passage portion in thermal contact with said optical
source is separated from an external surface of said mount by a
distance less than about 2 cm.
32. The method of claim 31 further comprising: a. collecting said
fluid sample from said outlet passage at an exhaust port; and b.
introducing at least a portion of said fluid sample collected at
said exhaust port to said sample chamber.
33. The method of claim 31, wherein said outlet passage in thermal
contact with said optical source comprises a heat sink.
34. The method of claim 33, wherein said heat sink comprises
conduits attached to a plurality of heat transfer passages in said
optical source mount for providing said exhaust flow to said heat
transfer passages.
35. The method of claim 30, wherein said outlet passage in thermal
contact with said optical source comprises a plenum.
36. The method of claim 35, wherein said plenum comprises a plenum
surface in thermal contact with said optical source, said surface
having a surface area that is greater than 650 mm.sup.2.
37. The method of claim 30 further comprising: a. directing a
portion of said exhaust flow to a heat-generating device to provide
cooling of said optical source and said heat-generating device.
38. A method of making a self-cooling particle sensor comprising:
a. providing an optical source in optical contact with a sample
chamber; b. providing an outlet passage that collects at least a
portion of sample fluid from said sample chamber; and c.
configuring said outlet passage such that said sample fluid within
said outlet passage thermally contacts said optical source to
provide self-cooling of the particle sensor.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit under 35 U.S.C. 119(e)
of U.S. Provisional Patent Application No. 60/896,649 filed on Mar.
23, 2007.
BACKGROUND OF THE INVENTION
[0002] The invention is generally in the field of optical particle
sensing and provides systems and methods for cooling optical
sources used in optical particle sensors. The cooling systems of
the present invention substantially increase the operating life of
optical sources, such as a laser, within the sensor and are
relatively inexpensive and simple to incorporate into an optical
particle sensor.
[0003] Optical particle sensors and counters are useful in a
variety of industrial applications where it is important that the
purity of materials used in a process be continuously monitored.
For example, in semi-conductor and other clean-room settings, or
industries requiring sterile and pure production (e.g.,
pharmaceuticals), material fluids that are used to make the end
product are continuously monitored to ensure adequate purity and
that any unwanted particles suspended in the fluid is within an
acceptable tolerance range. It is particularly advantageous to
rapidly identify when a fluid is contaminated with unwanted
particles so that the process can be stopped at an early stage,
thereby avoiding wasteful manufacture of defective product.
[0004] The importance of particle monitoring sensors is reflected
in the continuous and ongoing improvement and development of these
devices to improve reliability and throughput and to enable
detection and characterization of particles having smaller sizes.
In particular, particle measuring devices and particle sensors are
becoming more sophisticated, capable of detecting sub-micron
particles at higher fluid sampling rates (e.g., 1 CFM and higher).
This improvement is at least partly a result of incorporation of
more powerful optical sources such as laser diodes and diode arrays
capable of delivering high radiant powers to samples subject to
analysis. Optical sources that illuminate samples with high radiant
power also, however, generate a substantial amount of heat. Studies
indicate that laser operating life doubles for about every
10.degree. C. drop in operating temperature. Accordingly, it is
vital that optical particle counters with high energy optical
sources be thermally managed in a manner compatible with clean room
manufacturing processes. Prolonging optical source lifetime
provides cost-savings beyond simply avoiding optical source
replacement. Longer optical source lifetime increases process
reliability and decreases process downtime. These advantages arise
by avoiding unnecessary calibration that is required when an
optical source within the sensor is replaced, or the entire sensor
replaced. In addition, effective cooling of optical sources in
particle counters provides a more reliable light output, thereby
reducing noise and enhancing detection. The thermal management and
control of the present invention results in improved measuring
device capabilities and reliability.
[0005] Cooling mechanisms commonly used for optical sources in
particle counters include active thermoelectric cooling which often
require a substantial amount of power. For example, for a particle
sensor requiring 13 W of energy to deliver 1.6 W of laser power
from a laser diode, about 7 W of the 13 W total is for cooling the
laser to a 20.degree. C. delta temperature (US Pat. Pub.
2006/0038998). Although sample fluid has been used to cool an
aperture element associated with the optical communication between
the optical source and sample within a sample chamber (U.S. Pat.
Pub. 2006/0038998), flow of exhaust sample fluid has not been used
to directly cool an optical source. Other strategies for
controlling the temperature of optical sources in optical particle
sensors includes the use of a variety of device components that are
separate from the exhaust fluid, including by heat sinks, powered
cooling systems (U.S. Pat. Nos. 6,690,696; 6,091,494; 5,134,622)
and forced air systems (U.S. Pat. No. 5,029,335).
[0006] Another need in the art relates to particle measuring
devices that are associated with certain manufacturing processes
common in clean room manufacturing and high-purity settings (e.g.,
semi-conductor or pharmaceutical manufacture). Such clean rooms
require minimum case openings to ensure that access to the
measurement instrument does not constitute a significant source of
contaminants to the monitored environment. In addition, minimizing
case openings facilitates easier biological cleaning and room
decontamination, including cleaning and decontamination of the
particle sensor. Accordingly, standard cooling techniques such as
enclosure fans are inappropriate for these applications. The
invention addresses the need in the art for cooling mechanisms that
are capable of supplying adequate cooling and are not prone to
these contamination issues.
[0007] The problem of heat generation by an optical source is
generally recognized (e.g., U.S. Pat. Nos. 6,091,494; 5,029,335;
6,690,696), and accordingly heat dissipating means are generally
provided with such optical sources. The available solutions,
however, suffer from one or more limitations of complexity,
expense, undesirable additional energy requirements, or are
incompatible with the particle sensors of the present invention.
Although particle sensors may have some residual cooling attributed
to the fact that relatively cool sample fluid flows through the
sample chamber that interacts with the optical source, they suffer
from the limitation of not being able to adequately cool the
optical source. Accordingly, those sensors generally require an
active cooling mechanism to avoid excessive optical source
operating temperature.
[0008] As will be understood from the forgoing description, optical
particle sensors having thermally controlled optical sources are
needed, particularly optical particle sensor having cooled optical
sources exhibiting enhanced operating lifetimes. An additional need
is for systems for providing thermal control of these sensors that
do not require substantial additional power input. Furthermore, the
thermal control in these sensing systems should be readily
incorporated into optical particle sensors currently in use without
a need for unduly excessive additional design and expense.
SUMMARY OF THE INVENTION
[0009] The present invention provides systems and methods for
cooling one or more heat-producing elements within an optical
particle sensor or sensing system. Methods and systems of the
present invention use exhausted sample fluid conducted through
regions of the optical particle sensor to provide effective thermal
management, such as cooling, of selected device components. In some
embodiments, for example, exhaust from an optical particle sensor
is brought into thermal contact with a heat-producing element, such
as an optical source. Transfer of thermal energy to the exhaust
flow is used in the present invention to cool selected heat
generating device components so as to reduce their operating
temperature, thereby enhancing operating lifetime and performance
of these components. The exhausted sample fluid in thermal contact
with the heat producing element(s) is subsequently removed from the
optical particle sensor so as to dissipate heat and provide thermal
management of the sensing system.
[0010] Cooling strategies of the present invention utilize a
temperature differential between the sample fluid introduced into a
particle sensor and one or more heat-producing elements of the
sensing system to provide targeted device component cooling. In
particular, cooling of the heat-producing element is optionally
passive, thereby minimizing or avoiding a need for active
power-consuming cooling devices, such as thermoelectric cooling
devices. Systems and methods of the present invention are
particularly well suited for applications wherein low power
consumption is advantageous, such as optical particle sensors that
are part of a factory-integrated monitoring system, including
sensors powered by a DC battery of low voltage and current.
[0011] Disclosed herein are basic particle sensor configurations
combined with fluidic structures for cooling optical sources in
sensor systems. In an embodiment, a flowing sample fluid is
introduced into a sample chamber for optical analysis. After the
sample has been optically analyzed in the sample chamber, sample
fluid is removed and circulated along one or more specific fluidic
pathways selected to establish thermal contact with a heat
producing optical source element. In an aspect, substantially all
the sample fluid is used to cool a heat-generating device. In
another aspect, only a portion of the sample fluid is used to cool
a heat-generating device, such as a portion of the sample fluid
that is not required for cooling being exhausted to the
environment. Alternatively, a first portion of sample fluid is
directed to cool a first heat-generating device and a second
portion of sample fluid is directed to cool a second
heat-generating device. Alternatively, a plurality of
heat-generating devices are cooled in series by a single flow-path
of sample fluid such as essentially all the sample fluid or a
portion of the sample fluid, as desired, depending on operating
conditions and temperatures. Fluidic structures useful for
establishing thermal contact include, but are not limited to,
plenum chambers, air flow cavities, and optionally heat sink
structures, or any combination thereof. Heat transfer provided by
circulating exhausted sample fluid that is of a lower temperature
than the temperature of the optical source provides cooling of the
optical source without the need for any additional power or complex
device configurations. Accordingly, the invention provides an
elegant, versatile and reliable mechanism for maximizing optical
source lifetime in a particle sensor by reducing operating
temperatures.
[0012] In an embodiment, the invention provides an optical particle
sensor system for sensing particles in a fluid sample. The sensor
has a sample chamber with an inlet orifice for receiving a flow of
fluid sample and an outlet orifice for conducting the fluid sample
out of the sample chamber. As used herein, sample chamber refers to
a component of the optical particle sensor where fluid sample is
optically analyzed to characterize or detect particles within the
fluid. The sensor includes an optical source that is in optical
communication with the sample chamber. An outlet passage is
provided in fluid communication with the outlet orifice of the
sample chamber such that it receives flow of fluid sample exiting
the sample chamber. Sample fluid that exits the sample chamber is
referred to as exhaust sample fluid. The outlet passage is
configured to have a portion in thermal contact with the optical
source, thereby facilitating thermal exchange between the flow of
sample fluid within the outlet passage and the optical source. This
thermal exchange results in optical source cooling. Although the
invention can be used to cool any heat-producing element, one major
heat-producing element in these types of particle sensors is the
optical source. In an aspect, the optical source or optical source
is a high power optical source, such as a laser having a power
consumption that is equal to or greater than about 100 mW, such as
a laser optical source with an optical power in the range of 15 mW,
corresponding to an energy requirement of about 150 mW. In another
embodiment, the instrument is run at about 30-50 mW optical energy
from a diode consuming about 300-500 mW of power.
[0013] During sensor operation, the optical source has an operating
temperature. Thermal exchange between the flowing sample fluid in
the outlet passage and the optical source results in optical source
operating temperatures that are lower than a corresponding optical
source operating temperature that is not in thermal contact with
flowing sample fluid in an outlet passage. In an aspect, the flow
of sample fluid in the outlet passage is capable of maintaining the
operating temperature of the optical source to within about
5.degree. C. of the fluid being sampled as compared to a 10.degree.
C. to 15.degree. C. rise in the typical instrument internal
temperature during operation of a device without sample fluid
cooling. The cooling effect is even more pronounced in a common
configuration where a remote sample may be 10.degree. C. to
15.degree. C. less than the ambient temperature surrounding the
measurement instrument. Each 10.degree. C. of additional
temperature reduces the life of a laser diode by about 50%.
[0014] Because the magnitude of thermal transfer is related to the
temperature differential between the two elements in thermal
contact, an aspect of the invention is capable of being further
described by a variety of temperature ranges at different locations
throughout the sensor, sample fluid, and environment surrounding
the sensor. In an aspect, the fluid sample at the sample chamber
outlet has a temperature selected from a range of between about
20.degree. C. and about 30.degree. C. In an aspect, the temperature
of the flowing sample fluid in the outlet passage, including the
portion of the outlet passage in thermal contact with the optical
source, is about of the same temperature as the fluid sample
temperature in the sample chamber or fluid inlet, as there is very
little dwell time between the inlet and this cooling area and
therefore, minimal opportunity for the fluid to undergo a
significant change in temperature.
[0015] The flow-rate of the sample fluid through the outlet passage
is another parameter useful in the present systems and methods for
providing effective cooling. The particular flow-rate depends on
the characteristics of the system, including the geometry and
dimensions of the portion in thermal contact, the heat capacity
characteristics of the fluid, whether the fluid is liquid or gas,
and the amount of heat dissipation required. Although the methods
and systems of the present invention can utilize any flow-rate that
provides adequate heat transfer for the particular application, in
an aspect the outlet passage is capable of transmitting the flow of
fluid sample at flow rates selected from the range of between about
25 L/min or 28.3 L/min (1 cfm) and 100 L/min.
[0016] Another physical parameter useful in the present systems and
methods for optimizing heat exchange and cooling is the pressure of
the flowing sample fluid in the portion of the outlet passage in
thermal contact with the optical source. In an aspect, any of the
sensors have a chamber pressure in the sample chamber and an outlet
pressure in the outlet passage, wherein the chamber pressure and
the outlet pressure are within about 10% of each other. In an
aspect, the pressure drop in the outlet passage is minimized to
control or minimize power consumption from the pump source.
[0017] In an aspect sensors of the present invention have a
mounting element that supports the optical source, and specifically
assists in reliably positioning the optical source with respect to
the sample chamber. Because of the device geometry and connection
between the mounting element and the optical source, the mounting
element is in thermal contact with the optical source. In an
aspect, a portion of the outlet passage is in physical contact with
a mounting element supporting an optical source of an optical
particle sensor of the present invention. In addition, the mounting
element is provided in physical contact with the outlet passage and
the flowing sample fluid within the outlet passage. This intimate
connection enhances thermal exchange between the optical source and
flowing sample fluid in the outlet passage via the mounting
element.
[0018] Optical particle sensors of the present invention optionally
have a plurality of outlet passage portions in thermal contact with
the optical source. In an aspect, the sensor is capable of cooling
a second heat-generating device with the outlet passage having a
second portion in thermal contact with the heat-generating device.
The outlet passage optionally cools two or more heat-generating
devices in a serial flow path geometry. Alternatively, the outlet
passages cools two or more heat-generating devices in a parallel
flow-path geometry (e.g., simultaneously) by a junction that splits
the flow-stream from a single outlet flow-path into two or more
flow-paths. Any heat-generating device is amenable to cooling by
the mechanisms and devices disclosed herein, including a
heat-generating device selected from the group consisting of a
power source, motor, pump, optical component, blowers, blower
motor, regenerative blower, and fan.
[0019] In an aspect, the outlet passage portion in thermal contact
with the optical source or with the mounting element is a plenum.
Exhaust sample that exits the sample chamber enters the plenum.
This flowing exhaust sample in the plenum has a temperature that is
lower than the operating temperature of the optical source, such
that flowing exhaust sample in the plenum is capable of thermally
regulating the optical source. Accordingly, the plenum contains a
volume of flowing sample fluid for cooling the optical source. In
an embodiment, the plenum has a shape selected to maximize the
surface area of the plenum in thermal contact with the optical
source. Flowing exhaust sample in the plenum exits the plenum and
is conveyed out of the optical particle sensor body. This flux of
exhaust sample through the plenum provides the capability of
continuous thermal management of the optical source, and any other
components in thermal contact with the plenum.
[0020] In an aspect, the invention is further characterized by
expressing flow-rate, fluid properties, and geometrical dimension
in terms of a dimensionless constant, such as a Reynolds number
(Re). In an embodiment, the flowing sample fluid in the plenum is
turbulent or substantially turbulent. In an alternative embodiment,
the flowing sample fluid in the plenum is laminar Flow is
substantially turbulent for a plenum that has fluid mixing or
turbulence at least in the region immediately surrounding the
plenum face positioned closest to the optical source or the optical
source mount. More specifically, the fluid sample within the plenum
can have a Re of 2300 for turbulent flow. In an embodiment, the
fluid sample within the plenum can have a Re of between about 2200
and 2900 for substantially turbulent or turbulent flow. In an
embodiment, the fluid sample within the plenum can have a Re of
about 2000 for laminar flow. In an aspect, any one or more of the
physical or geometric parameters of pressure, temperature, flow
rate, surface area in thermal contact shape and/or position are
selected to provide adequate cooling of the optical light
source.
[0021] Any of the sensors optionally have a plenum with at least
one surface that corresponds to the optical source mount exterior
surface. Such shared surface(s) assist in facilitating more
efficient heat exchange between the optical source/mount and the
flowing sample fluid within the plenum. Preferably, the surface
area of this plenum wall is relatively large to further increase
heat exchange, corresponding to greater than about 10 times the
surface area of an optical source that is a laser diode. In an
aspect, the plenum surface that corresponds to the optical source
mount exterior surface has a surface area greater than about 650
mm.sup.2.
[0022] Plenums of systems and methods of the present invention
optionally have a pair of orifices for introducing and removing
flowing fluid sample to and from the plenum. Inlet tubing having a
first end connected to the plenum inlet orifice and a second end
connected to the sample chamber outlet facilitates introduction of
fluid sample to the plenum. Alternatively, the inlet tubing may
connect to the outlet passage at a position downstream of the
sample chamber outlet. Outlet tubing having a first end connected
to the plenum outlet orifice and a second end connected to an
exhaust orifice facilitates removal of flowing fluid sample from
the plenum and out of the sensor.
[0023] In an aspect, the temperature of the fluid sample at the
plenum inlet orifice is about 5.degree. C. to about 10.degree. C.
less than the optical source operating temperature.
[0024] Any of the sensors optionally have a plurality of plenums,
wherein each plenum is in thermal contact with the optical source.
This can be particularly useful for optical sources that have a
tendency to generate excessive heat that must be dissipated. A
plurality of plenums is also useful for optical source mounts
having a plurality of exterior faces, wherein a plenum is paired
with a mount face.
[0025] In an embodiment, the outlet passage portion in thermal
contact with the optical source is a heat sink with an inlet heat
sink orifice and outlet heat sink orifice. In this embodiment, the
fluid sample at the inlet heat sink orifice has an inlet
temperature, wherein the inlet temperature is less than the optical
source operating temperature. Accordingly, the lower temperature of
flowing sample fluid in the heat sink provides cooling of the
optical source. In an aspect, the heat sink comprises one or more
heat transfer passages. In an aspect, the heat transfer passage has
a geometric shape selected from the group consisting of a spiral,
fin, chamber, rectangular bore and circular bore.
[0026] In an embodiment, the invention has a plurality of heat
transfer passages that are connected in a parallel, series, or
parallel and series configuration to the inlet heat sink orifice
and the outlet heat sink orifice. In this embodiment, flowing
sample fluid is introduced and removed from each of the heat
transfer passages such that the flowing sample fluid within the
heat transfer passage is capable of conveying heat generated by the
optical source. The "heated" sample fluid is transported to the
exhaust outlet and removed from the sensor, thereby cooling the
optical source. The portion in thermal contact with the optical
source or mount is optionally described as having a horizontal
surface footprint, with larger footprints providing the ability to
dissipate more heat. In an aspect, the heat sink comprises tubing
capable of transporting the sample fluid.
[0027] The magnitude of heat transfer is also affected by the
separation distance of the heat generating element (e.g., an
optical source) and the heat dissipating element (e.g., the flowing
sample fluid within the portion of the outlet passage in thermal
contact with the optical source). In an aspect, the outlet passage
portion in thermal contact is separated from the optical source by
a separation distance ranging up to about 2 cm.
[0028] Systems and methods of the present invention are designed to
thermally manage optical sources in optical particle sensor devices
by dissipating heat generated by the optical source. In an
embodiment, the cooling mechanism is capable of dissipating or
removing sufficient heat to maintain an about 100 mW or greater
powered optical source at an operating temperature that is about
5.degree. C. to 15.degree. C. less than the operating temperature
of an optical source in a sensor without a fluid sample exhaust
cooling. "Conventional sensor" refers to a sensor that does not
have a fluid sample exhaust cooling mechanism of the present
invention.
[0029] In another aspect, the outlet passage is configured to have
a cross-flow geometry relative to the optical source. "Cross-flow
geometry" refers to a flow path that traverses from one side of the
optical source to the corresponding opposite side of the optical
source. For robust heat exchange, the flow path is optionally split
so that substantially the entire surface area of the optical source
is in good thermal contact with the flowstream, such as that
depicted in FIG. 2E-2F, for example.
[0030] An alternative embodiment of the invention provides an
airflow-cooled particle measuring device. The device has an optical
source for generating electromagnetic radiation for detecting
particles and an optical source mount for connecting the optical
source to the particle counter. An airflow cavity transports air
for cooling the optical source, wherein the airflow cavity is in
thermal contact with the optical source. In an embodiment, the
airflow cavity comprises a plurality of channels in the optical
source mount. Alternatively, the airflow cavity is a shaped air
plenum. In an aspect the airflow cavity is the volume space defined
between the exterior surface of the optical source and the
inward-facing surface(s) of the source mount. In another aspect,
the airflow cavity comprises tubing in which airflow is
constrained.
[0031] In an aspect, the transported air has a flow rate selected
from a range of between about 0.5 cfm to about 1.5 cfm. In an
aspect, the device further comprises means for forcing air through
said airflow cavity. Means for forcing airflow through the cavity
is known in the art, and includes fans, pumps, vacuum sources that
are operably connected to the airflow cavity.
[0032] In an aspect, the invention is a method of cooling an
optical source or a particle sensor. The method of cooling an
optical source involves providing a particle sensor that has a
sample chamber with an inlet orifice for receiving an input flow of
at least a portion of fluid sample and an outlet orifice for
conducting an exhaust flow fluid sample out of the sample chamber.
An optical source is provided in optical communication with the
sample chamber. An outlet passage is provided in fluid
communication with the outlet orifice of the sample chamber for
receiving the exhaust flow of the fluid sample from the sample
chamber. The outlet passage has a portion in thermal contact with
the optical source. Cooling occurs by flowing the fluid sample
through the sample chamber and the outlet passage, thereby
generating input flow of sample fluid and exhaust flow of sample
fluid to provide thermal exchange between exhaust flow of sample
fluid flowing through the outlet passage and the optical source.
This thermal exchange results in optical source cooling. In an
aspect, a portion of said exhaust flow is directed to provide
cooling of another heat generating device, such as a blower motor,
for example. In an aspect this cooling is in a parallel
configuration wherein separate exhaust flow-streams achieve
separate cooling of the optical device a second heat-generating
device (referred herein as "simultaneous cooling"). Alternatively,
a serial configuration flow-path provides for cooling of the
optical source and the other heat-generating device(s) by a single
flow-stream. In an aspect a total of two heat-generating devices
(including the optical source) are cooled. In an aspect, three or
more heat-generating devices are cooled.
[0033] The optical source is optionally connected to the particle
counter by an optical source mount, and the outlet passage portion
in thermal contact with the optical source is separated from an
external surface of the mount by a distance less than about 20 mm.
Any of the devices, sensors or methods of the present invention can
have an optical source that is a laser diode.
[0034] In the context where it may be necessary to continuously
analyze a given fluid sample, or repeat sample measurements on a
given sample fluid volume, the method further comprises collecting
the fluid sample from the outlet passage at an exhaust port and
introducing at least a portion of the collected fluid sample to the
inlet orifice of the sample chamber.
[0035] In the embodiment where the heat sink comprises passages,
the passages optionally have a luminal area. In another embodiment,
the exhaust flow through the outlet passage has a volumetric
flow-rate selected from the range of about 1 cfm (28.3 L/min) to
about 100 L/min.
[0036] In an embodiment, the invention is a method of cooling a
particle sensor by providing an optical source in optical contact
with a sample chamber and an airflow cavity in thermal contact with
the optical source, wherein the airflow cavity is capable of
facilitating airflow. This airflow dissipates heat build-up by the
optical source, thereby cooling said particle sensor.
[0037] Any of the cooling methods may use any of the presently
disclosed particle sensors. In an embodiment, the invention is a
method of making a self-cooling particle sensor by providing an
optical source in optical contact with a sample chamber and an
outlet passage that collects at least a portion of sample fluid
from the sample chamber. Configuring the outlet passage such that
the sample fluid within the outlet passage establishes thermal
contact with the optical source provides self-cooling of the
particle sensor.
[0038] In an embodiment, the surface temperature of a surface in
thermal contact with the outlet passage is preferably no greater
than about 5.degree. C. or about 2.degree. C. above sample volume
temperature. To avoid condensation on the surface in thermal
contact, its temperature is maintained above the dewpoint
temperature of air within the body of the particle counter.
[0039] In an embodiment, the outlet passage that is in thermal
contact with a surface whose heat is being dissipated is a shaped
heat sink or exchanger having a serpentine passage with outlet
fluid sample flowing therethrough.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] FIG. 1 is a schematic of a particle sensor having a plenum
to facilitate cooling of an optical source.
[0041] FIG. 2 illustrates various heat sinks positioned relative to
an optical source. A End view of source and heat sink. B Side view.
C. End view of illustrating various heat passages in a heat sink
that is part of a mount for optical source. D Side view of optical
source illustrating heat source having a fin geometry. E Top view
of a cross-flow geometry of sample fluid cooling optical source
with a plurality of heat transfer passages overlaying an optical
source. F is a cross-section of optical source with a heat sink
flow passage in intimate contact for maximizing heat exchange
between optical source and sample fluid within the heat sink flow
passage.
[0042] FIG. 3 is a sensor that cools an optical source and a second
heat-generating device.
[0043] FIG. 4 illustrates a sensor having tubing for conveying
sample fluid.
[0044] FIG. 5 illustrates a cross-flow sensor with split
exhaust.
[0045] FIG. 6 is a side-view of a self-cooled sensor.
[0046] FIG. 7 is a selective cut providing a cross-section
corresponding to each level of the flow-path (depicted as arrows
within flow-path) of the sensor in FIG. 6. The cut in the central
portion exposes a motor cover. The lower portion shows the vanes of
the blower as they are exposed.
[0047] FIG. 8 is a front perspective view of the self-cooled sensor
of FIG. 6 showing the laser module.
[0048] FIG. 9 is a rear perspective view of the self-cooled sensor
of FIG. 6 showing the blower entry and exhaust ports.
[0049] FIG. 10 is a side perspective view of the self-cooled sensor
of FIG. 6.
DETAILED DESCRIPTION OF THE INVENTION
[0050] "Particle sensor" refers to a device that is capable of
providing information about particles suspended within a fluid. The
fluid can be liquid or gas phase. The particles can be constrained
or unconstrained within the fluid. Examples of particle information
generated by such sensors include counts, concentration, size, size
distribution, shape or other information generated by interaction
of the optical source with the particle (e.g., fluorescent
signal).
[0051] "Optical source" refers to a device or device component that
is capable of delivering electromagnetic radiation to a sample. The
term is not limited to visible radiation, such as by a visible
light beam, but is used in a broad sense to include any
electromagnetic radiation. The optical source may be embodied as a
laser or laser array, such as a diode laser, diode laser array,
diode laser pumped solid state laser, LEDs, LED arrays, gas phase
laser, solid state laser, to name a few examples. "Optical
communication" refers to an interaction (or lack of an interaction)
between the output of the optical source and one or more particles
in the fluid sample positioned within the sample chamber that
provides useful and quantifiable information about the sample.
[0052] "Outlet passage" refers to a conduit that conveys fluid
sample from the sample chamber for the purpose of cooling a
heat-producing element such as an optical source. The optical
passage may be connected directly or indirectly to the sample
chamber. An example of a direct connection is an outlet passage
that has one end attached to the sample chamber outlet orifice. An
indirect connection includes connection to a sample
fluid-containing location at a point downstream from the sample
chamber. For example, the outlet passage can be connected to an
intervening passage or tubing connected to the sample chamber. Any
connection that provides "fluid communication" between the outlet
passage and sample chamber can be used in the present invention.
"Fluid communication" refers to fluid within the sample chamber
that is capable of being conveyed to and through the outlet passage
to provide cooling. In particular, cooling is provided by
positioning a portion of the outlet passage with respect to a
heat-generating device so that "thermal contact" is established
between the two.
[0053] "Thermal contact" refers to one element being capable of
affecting the operating or steady-state temperature of another
element by removing heat from the element. In the present invention
a cooling fluid, such as sample fluid that is within an outlet
passage is capable of conducting heat from the optical source and
out of the particle sensor and conveying "heated" sample fluid out
of the particle sensor. Two elements in thermal contact facilitate
"thermal exchange" from the element having a higher temperature to
the element having a lower temperature, such as from an optical
source to a sample fluid. Two elements in thermal contact need not
be in direct physical contact. For example, the materials can be
separated by a material, preferably by a material exhibiting high
thermal conductivity, such as a metal (e.g., aluminum or copper),
thermal grease or a thermally conductive pad. For example, the
cooling sample fluid within the outlet passage is said to be in
thermal contact with the optical source although the sample fluid
is physically separated from the optical source by an optical
source mount and optionally by other materials such as the outlet
passage wall (for the embodiment where exhaust fluid is contained
within walled passages such as tubing). Thermal contact may also
refer to a fluid that is in direct physical contact with a
heat-producing element, such as fluid (e.g., air) within a fluid
(e.g., airflow) cavity that surrounds an optical device.
[0054] "Optical source mount" or "mounting element" refers to the
manner in which one element (e.g., optical source) is positioned
and held within the sensor. Mount is used broadly to refer to any
structural element of the device, and particularly elements having
high heat-conducting properties such as a metal. At least a portion
of the material separating the outlet passage and surface in
thermal contact is made of a material having good heat-transfer
characteristics, e.g., metal, aluminum or copper. Optionally, the
interior facing surface of the outlet passage is coated with a
chemically-inert material to minimize chemical reaction of sample
fluid within the outlet passage with a heat-conducting surface that
may be less chemically-inert with the fluid sample.
[0055] The ability of the fluid sample within the outlet passage to
provide cooling of a heat-producing source such as an optical
source depends on a number of factors. One factor is the flow-rate
and flow-characteristics of the fluid sample. Accordingly, the
outlet passage is capable of transmitting flow of fluid sample at
appropriate flow-rates, including user-selected flow-rates.
"Transmitting flow" refers to the amount of sample fluid that is
flowing into and correspondingly exiting, the outlet passage. This
flow can be quantitatively expressed in any manner such as a
volumetric flowrate, average fluid velocity, as well as
incorporated into dimensionless variables such as a Reynolds
number.
[0056] The Reynolds number (Re) is the ratio of inertial to viscous
forces in a flowing system and is calculated by: Re=.rho.VD/.eta.,
where .rho. is the fluid density, V is the average velocity, D is a
characteristic length such as channel diameter, width or length,
and .eta. the fluid viscosity. Re is useful in describing whether a
fluid flow is turbulent or laminar. In general, a Re less than
about 2000 is considered laminar, but the precise cut-off is
variable depending on flow conditions, geometry and perturbations
to the system. Because laminar flow tends not to mix (except by
diffusion), in the heat exchange context of the present invention
it is generally preferable that the fluid sample flow in the region
where thermal contact and exchange is desired be substantially
turbulent with Re, for example, greater than about 2000, 2500-4500,
or about 3000-4000. Adequate mixing of fluid flow to ensure
increased heat exchange can be further facilitated by incorporating
baffles or other flow-disturbing elements within the outlet
passage.
[0057] The pressure within the outlet passage is another parameter
associated with heat exchange between the fluid sample within the
outlet passage and the optical source. In general, especially for
gas state fluids, higher pressures facilitate greater heat
exchange. The "pressure difference" between the sample chamber and
outlet passage refers to the difference between the average
pressure within the sample chamber and the outlet passage. This
pressure difference is generated by any means known in the art
including a vacuum source or a fluid pump. Unless a pressure is
specified for a specific location, the pressure refers to an
average pressure within the component.
[0058] An outlet passage in "physical contact" with a mounting
element refers to there being no intervening material between the
fluid sample coolant and mount surface, except for an optional thin
layer of chemically-inert material. For example, an outlet passage
further comprising channels directly in the mounting element of a
plenum having at least one surface that is the outer surface of the
mounting element is said to be in physical contact with the
mounting element.
[0059] A "plenum" refers to that portion of the outlet passage
having a specially designed volume in which heat exchange is
maximized. Preferably, a plenum has at least one surface
corresponding to the optical source mount to provide maximum heat
exchange between the optical source and the sample fluid within the
plenum. This surface can be further shaped to contain a plurality
of channels of different shapes and orientation to facilitate heat
exchange. The plenum volume refers to the volume defined by the
plenum walls and plenum inlet(s) and outlet(s).
[0060] "Heat sink" refers to a region of the outlet passage,
including a separate component connected to the outlet passage,
designed to enhance heat exchange. Such a heat sink provides an
ability to more precisely tailor the passage geometry of cooling
fluid flow compared to a plenum. In particular, the heat sink can
have any number of individual heat exchangers such as a plurality
of self-contained or inter-connected passages and/or chambers
within the optical source mount. In contrast to a plenum, a heat
sink can be entirely contained within a to-be-cooled material. The
passages can be configured to be straight-lines, curved, serpentine
or any combination thereof. Alternatively, the passages can
comprise tubing that is not integrally contained within the
mount.
[0061] Any of the elements in thermal contact can be described with
a "thermal exchange surface footprint." This footprint refers to
the surface area of the mount in physical contact with the cooling
sample fluid. Accordingly, a plenum with a surface that corresponds
to a smooth mount face has a smaller thermal exchange surface
footprint than a plenum having channels (e.g., radiating fins)
etched into the mount face.
[0062] "Operating temperature" refers to a steady state temperature
an optical source would achieve during use. Accordingly, the
operating temperature of an optical source without the cooling
embodiment of the present invention is higher than the operating
temperature of an optical source incorporated into a device of the
present invention.
[0063] "Exhaust" or "exhaust sample fluid" refers to flowing sample
fluid that has exited the sample chamber. The exhaust is used to
cool a heat-producing element by ensuring that at least a portion
of flowing exhaust is in thermal contact with the heat-producing
element and capable of thermal exchange to cool the heat-producing
element.
[0064] In addition to providing cooling of an optical source, the
present invention is capable of cooling other elements that tend to
generate heat, including but not limited to power supplies, pump
motors, or fans, to name a few examples.
[0065] All references cited throughout this application, for
example patent documents including issued or granted patents or
equivalents; patent application publications; and non-patent
literature documents or other source material are hereby
incorporated by reference in their entireties, as though
individually incorporated by reference, to the extent each
reference is not inconsistent with the disclosure in this
application (for example, a reference that is partially
inconsistent is incorporated by reference except for the partially
inconsistent portion of the reference).
[0066] Every formulation or combination of components described or
exemplified herein can be used to practice the invention, unless
otherwise stated. All patents and publications mentioned in the
specification are indicative of the levels of skill of those
skilled in the art to which the invention pertains. References
cited herein are incorporated by reference in their entirety to
indicate the state of the art as of their publication or filing
date and it is intended that this information can be employed
herein, if needed, to exclude specific embodiments that are in the
prior art. Whenever a range is given, such as a temperature, size,
pressure, Re, or time range, all intermediate ranges and subranges,
as well as all individual values included in the ranges given are
intended to be included in the disclosure.
[0067] As used herein, "comprising" is synonymous with "including,"
"containing," or "characterized by," and is inclusive or open-ended
and does not exclude additional, unrecited elements or method
steps. As used herein, "consisting of" excludes any element, step,
or ingredient not specified in the claim element. As used herein,
"consisting essentially of" does not exclude materials or steps
that do not materially affect the basic and novel characteristics
of the claim. In each instance herein any of the terms
"comprising", "consisting essentially of" and "consisting of" may
be replaced with either of the other two terms. The invention
illustratively described herein may be practiced in the absence of
any element or elements, limitation or limitations which is not
specifically disclosed herein.
[0068] One of ordinary skill in the art will appreciate that,
materials and methods other than those specifically exemplified can
be employed in the practice of the invention without resort to
undue experimentation. All art-known functional equivalents, of any
such materials and methods are intended to be included in this
invention. The terms and expressions which have been employed are
used as terms of description and not of limitation, and there is no
intention that in the use of such terms and expressions of
excluding any equivalents of the features shown and described or
portions thereof, but it is recognized that various modifications
are possible within the scope of the invention claimed. Thus, it
should be understood that although the present invention has been
specifically disclosed by preferred embodiments and optional
features, modification and variation of the concepts herein
disclosed may be resorted to by those skilled in the art, and that
such modifications and variations are considered to be within the
scope of this invention as defined by the appended claims.
EXAMPLE 1
Plenum-Cooled Particle Sensor
[0069] FIG. 1 is a schematic illustration of a particle sensor 10.
Referring to FIG. 1, a fluid sample 20 is introduced to a sample
chamber 30 at an inlet orifice 40. An optical source 60 illuminates
fluid sample within chamber 30 and information is collected and
analyzed to provide information about the status of fluid sample
20, as known in the art, such as scattering (forward and/or side),
intensity, emission spectra, etc. Fluid sample flows out of the
sample chamber 30 at an outlet orifice 50 and into outlet passage
70. Fluid sample exits the particle sensor 10 at an exhaust orifice
or port 190. The general path of flowing fluid sample 20 is
indicated by the arrow that transits the sample chamber 30 and
outlet passage 70.
[0070] In this example, the outlet passage 70 further comprises a
plenum 100 having a portion 80 in thermal contact with the optical
source 60. In an embodiment, optical source 60 is positioned within
the particle sensor 10 by a mounting element or optical source
mount 90. In an embodiment, the outlet passage 70, and more
particularly portion 80 of plenum 100 is in thermal contact with
mounting element or mount 90.
[0071] Plenum 100 optionally has a plenum inlet orifice 110 and a
plenum outlet orifice 120 for the introduction and exit of sample
flow to and from plenum 100, respectively. Plenum 100 is shaped to
have a volume and thermal exchange footprint that ensures maximum
heat transfer from the optical source 60 and/or mounting element 90
to flowing sample fluid within plenum 100. Heat transferred to
flowing sample fluid within plenum 100 is transported out of the
sensor 10 by sample flow exhaust 195 comprising flowing sample
volume from plenum 100 and out of the outlet passage 70 at exhaust
orifice 190, thereby generally cooling particle sensor 10, and
specifically optical source 60.
[0072] In an embodiment, the plenum 100 can be shaped and/or
replaced by a heat sink chamber 200 having an inlet heat sink
orifice 210 and an outlet heat sink orifice 220 to convey flowing
fluid sample to facilitate cooling of the optical source 60, such
as those illustrated in FIG. 2. The heat sink chamber optionally
comprises one or more heat transfer passages 230 through the
mounting element 90 to maximize heat transfer from the optical
source 60 (FIG. 2E).
[0073] To control the flow-rate of fluid sample within the outlet
passage 70, means for generating fluid flow is operably connected
to outlet passage 70. Any means known in the art for generating
fluid flow, including means having user-selected flow-rate
capability, may be used, including but not limited to pumps,
airflow pumps, centrifugal pumps, vacuum source, centripetal fans,
blowers.
[0074] A plenum as part of a heat-exchange mechanism is
advantageous because it can serve as part of the mounting element
90. Mount 90 assists in securing the optical source 60 to the other
parts of the particle sensor 10. A mounting element that is a part
of a plenum surface can reduce manufacturing complexity and cost.
In addition, the plenum and/or outlet passage can be configured and
positioned to cool other heat-generating areas within the particle
sensor, such as pumps, motors, detectors or power supplies. A
plenum that is physically connected to the mount element 90 refers
to a mount that provides structural integrity and/or geometric
constraint to the plenum 100, such as by defining a plenum surface.
This embodiment also maximizes thermal contact and exchange by
minimizing the separation distance between the mount 90 and plenum
100 as well as between the optical source 60 and plenum
surface.
[0075] As understood in the art, heat dissipation and associated
temperatures are numerically solvable for a variety of systems by
solving the heat equation with one boundary condition corresponding
to the temperature of the plenum surface in thermal contact with
the mount. This temperature is affected by the flowing sample fluid
coolant over the plenum surface and is, therefore, modeled by the
flow equation to account for flow characteristics and heat
convection. Another boundary condition is given by the operating
temperature of the optical source. The partial differential
equations arising from the geometry and conditions for a
plenum-cooled optical source with a 1 cfm fluid sample at
20.degree. C. flow rate through the plenum and a 30.degree. C.
optical source operating temperature have been numerically solved.
In silico experiments demonstrate the portion of a plenum in
thermal communication with an optical source provides significant
cooling of the optical source. Two orthogonal slices through the
center of the optical source are shown having a temperature
distribution ranging from 19.85.degree. C. to 28.85.degree. C. The
portion of the outlet passage in thermal contact with the optical
source remains at a temperature of about 20-21.degree. C., whereas
the opposite side of the optical source from the portion in thermal
contact has a temperature closer to 30.degree. C. The model is for
a 20.degree. C. environment and 30.degree. C. enclosure temperature
with a 1 cfm flow rate, indicating the laser diode maintains a
steady-state temperature of about 23.degree. C. during operation.
The cooling action of the flowing sample fluid results in a laser
diode operating temperature of 23.degree. C. This is significant
cooling as empirical observations indicate that laser life
approximately doubles for every 10.degree. C. decrease in operating
temperature. In addition, designs that do not provide the cooling
mechanism of the present invention have an optical source operating
temperature that is at least 3.degree. C. to 5.degree. C. above
ambient temperature. The computational experiment presented herein
provides useful information related to design parameters, including
appropriate flow conditions (flow-rate, Re), geometry (e.g.,
thermal contact shape, separation distance) and resultant cooling
temperatures for a variety of high-powered optical sources and
ambient temperature conditions.
EXAMPLE 2
Self-Contained Heat Sink Connected to Outlet Orifice
[0076] In an embodiment, a mounting element 90 with integral heat
sink 200 provides cooling, (see, for example, FIGS. 2 and 5). A
heat sink conduit 205 that provides sample fluid 20 to the heat
sink 200 is connected to the sample chamber outlet orifice 50, the
exhaust orifice 190, or to an outlet passage location between the
outlet orifice 50 and exhaust orifice 190. To transport fluid
sample to the heat sink, the heat sink passage is operably
connected to the means for generating fluid flow, such as vacuum
source or pump. In an aspect, the heat sink conduit comprises
tubing, including flexible tubing, connected at one end for
receiving sample fluid, such as to chamber outlet orifice 50,
outlet passage 70 or exhaust orifice/port 190 and at the other end
to inlet heat sink orifice 210 for introducing the fluid sample to
the heat sink.
[0077] The heat sink optionally comprises one or more heat sink
transfer passages 230 within the mounting element 90 through which
fluid sample flows for cooling the optical source 60 (see FIG. 2E).
In an aspect, the heat sink passages are configured to provide high
surface areas for thermal exchange with the mount 90. For example,
passages having a relatively large depth into the mount compared to
the width (e.g., width less than 50%, 30% or 10% of depth)
facilitate heat exchange without unduly impacting the mount
structural integrity. Such geometry is referred to as a "fin"
structure. Alternatively, the fin structure is oriented in the
opposite direction to facilitate heat exchange (e.g., depth less
than 50%, 30% or 10% of height); this orientation is referred to as
a "heat sink chamber." The heat sink can comprise any geometry such
as a plurality of these structures, including multiple fin and/or
chamber structures having different orientations.
[0078] Any of the heat exchange surfaces can be tailored to the
specific optical source mount 90 geometry. For example, a
multiple-sided mount can have multiple heat sinks (or plenums) to
provide increased heat transfer from each of the mount sides. A
mount with curved sides can have heat sinks, passages or plenums
230 with a similar curved orientation (see FIG. 2F).
[0079] The laser assembly heat sinks of the present invention do
not constrain the pump to any particular location within the
product housing. For example, a heat sink conduit comprising tubing
facilitates transfer of sample fluid coolant from any location to
the device that is to be cooled in a relatively simple and
cost-effective manner. The downstream end of the heat sink, e.g.,
the outlet heat sink orifice itself can be an exhaust port or can
also have a passage or tubing to transport the sample volume to an
appropriate location or connection within the particle sensor.
EXAMPLE 3
Airflow Cavity Within Mounting Assembly
[0080] An alternative cooling process relates to an airflow cavity
positioned between the optical source 60 and optical source mount
90. In this aspect, air is routed into and out of the cavity using
either tubing or a shaped air plenum. Although this aspect
eliminates one thermal interface (e.g., the air coolant is in
direct contact with the optical source), there is added complexity
and cost that is minimized for the embodiments that use the sample
fluid itself as the coolant. In this aspect, air is forced into the
cavity by any means known in the art such as a fan or pump.
EXAMPLE 4
Multiple Device Cooling
[0081] Provided herein are various configurations for cooling a
plurality of heat-generating devices within the sensor, and for
finer control of flows and flows into optional multiple flowpaths.
FIG. 3 illustrates a geometrical configuration of the outlet
passage 70 for cooling an optical source 60 and then a
heat-generating device 260, such as a blower motor. In this example
all the sample fluid collected at outlet orifice 50 flows along
outlet passage 70, plenum 100 for cooling optical source 60 and
then exits plenum 100 at plenum outlet 120 for subsequent cooling
of heat-generating device 260.
[0082] FIG. 4 provides another embodiment where outlet passage 70
further comprises a portion of inlet tubing 300 that introduces
sample fluid to plenum 100 at plenum inlet orifice 110. Outlet,
such as outlet conduit or tubing 310 removes sample fluid from the
plenum outlet orifice 120, thereby conveying sample from plenum 100
to exhaust orifice 190, such that heated exhaust sample fluid 195
is removed from sensor 10. In this example, optional plurality of
plenums (corresponding to 100 and a plenum positioned within tubing
300) can provide plurality of cooling tailored to specific sensor
locations, as necessary.
[0083] Another flowpath geometry for cooling multiple devices in
the sensor is provided in FIG. 5. In this embodiment, outlet
passage 70 comprises a junction 290 that splits outlet passage 70
into a first flowpath 510 and a second flowpath 520. FIG. 5 further
illustrates a cross-flow geometry 550 of that portion of outlet
passage 70 (e.g., flowpath 510) that cools optical source 60.
Examples of heat sinks for use in a "cross-flow" geometry include,
but are not limited to, those shown in FIGS. 2E and 2F In an
embodiment, flowpath 520 is exhausted to environment. In an
embodiment, flowpath 520 is directed to cool a heat-generating
device. In an aspect, the relative amounts of flow between flowpath
510 and 520 are regulated as needed, such as providing higher flows
to the path in need of greater heat dissipation, or for decreasing
flow when heat generation conditions are lower. This regulation can
be automated as known in the art such as by temperature sensors
operably connected to valves or flow-regulators that control flow
in each of 510 and 520.
[0084] Various views of one embodiment of a self-cooled sensor are
provided in FIGS. 6-10, showing various other features such as
related electronics, laser modules, blowers, etc.
REFERENCES
[0085] Particle counters, sensors and related optical sources and
configurations are known in the art and in which the present
invention may be incorporated, include but are not limited to U.S.
Pat. Nos. 7,088,447, 7,088,446, 7,030,980, 6,945,090, 6,903,818,
6,859,277, 6,709,311, 6,690,696, 6,615,679, 6,275,290, 6,246,474,
6,167,107, 6,091,494, 5,903,338, 5,861,950, 5,805,281, 5,751,422,
5,671,046, 5,493,123, 5,459,569, 5,282,151, 5,134,622, 5,029,335,
4,893,932, 4,893,928, 4,798,465, 4,740,988, 4,728,190, 4,636,075,
4,594,715, 4,571,079,4,027,162, 4,011,459, 3,941,982, U.S. Pub. No.
2006/0038998. These references are hereby incorporated by reference
in their entireties, as though individually incorporated by
reference, to the extent each reference is not inconsistent with
the disclosure in this application.
* * * * *